The present invention relates to a multifunctional ceramic sensor and technology with a single sensing element which is capable of detecting temperature, humidity and gas.
Recently, various special sensors have been used to detect the temperature, the humidity or the presence of gases in the surrounding atmosphere which are adapted for use in industry, agriculture, office, family and so on. So that bifunctional ceramic sensor have been developed. The p-type BaTiO.sub.3 -SrTiO.sub.3 and MgCr.sub.2 O.sub.4 -TiO.sub.2 used to sense or detect the temperature-humidity and the humidity-gas, respectively. The former has been using as a control device for air conditioners, driers and cookers but the latter for microwave ovens, cookers and roaster etc.
The difficulties of developing such multifunctional sensitive element are as follows. First, the sensitive elements are exposed to the air which contan not only the water vapor but also various gases and oils, this will inevitable cause physical and chemical changes on the sensitive elements, the gases, oil, dust and dirt etc. will adhere to the surfaces of the sensitive elements, whereby the sensitivity would be degraded. Second, the relative humidity is dependent on the temperature of the air varies over a wide range. Almost all of the materials respond to variations in relative humidity, but it is extremely difficult to provide a humidity sensitive element is capable of detecting the relative humidity from 1 to 100% over a wide temperature variation. Third, without the development of materials which are highly responsive to tempeature humidity and gases variations, multifunctional sensors of high reliability. Last but not the least, the multifunctional sensor is capable of detecting temperature-humidity-gas by physical or chemical parameters in the form of electric signals must not exhibite mutual cross-talk.
So far, there has not yet been devised and demonstrated a single sensing element which is capable of sensing trith the temperature-humidity-gas content in the surrounding atmosphere with a reliable degree of accuracy. As a result, the industrial systematization has been much delayed.